Wiper blades are well known in the prior art. by way of example the wiper blades, and in particular the pressure distributing rods and the corresponding wiping elements, disclosed in the following documents may be mentioned: the German (DE) patent application Nos. 2,223,898--2,324,701--2,344,876 and the French patent application No. 2,500,389.
The wiping element disclosed in said four patent documents have at least two common characteristics:
The wiping element comprises, in cross-section, a neck portion which acts as a hinge about the axis of which the lower portion of the wiping element may rock in order to follow the oscillating movement of the wiper arm of the wiper blade. PA1 The lower portion of the wiping element comprises, in cross-section, a triangular portion of which one of the sides is directed towards the pressure distributing rod and of which the edge opposite to said side is directed towards the surface to be wiped. PA1 to provide a wiper blade of which the wiping element does no longer comprise a hinge portion; PA1 to provide a wiper blade wherein the total volume of the wiping element is reduced to a minimum; PA1 to provide a wiper blade of which the wiping element can be easily extruded in a continuous manner; and PA1 to provide a wiper blade of which the configuration of the wiping element and of the pressure distributing rod guarantee a better wiping efficiency when the vehicle moves at high speed. PA1 (a) the vertical bar of said T is tapered in the direction opposite to the surface to be wiped, PA1 (b) the junction between the vertical and the horizontal bar of said T is realized by rounded curves, and PA1 (c) the upper portion of the wiping element is linked to the medium portion of the wiping element via a reduced portion which, in cross-section, is laterally limited by rounded curves.
The main disadvantages of the wiping element provided with a neck portion acting as a hinge are: (a) a considerable force is needed for obtaining the rocking movement of the lower portion of the wiping element, (b) in bad weather conditions the rocking movement of the lower portion of the wiping element risks to be irregular and (c) the neck or hinge portion is subject to the aging phenomenon, i.e. to becoming brittle with time, and thus have negative effects on the good functioning of the wiper blade.
Concerning the triangular portion of the lower portion of the wiping elements disclosed in the above mentioned patent documents it is to be noted that its function is to limit the rocking movement of said lower portion of the wiping elements in alternatively touching on both sides the bottom surface of the pressure distributing rods, as a function of the oscillating movement of the wiper arm of the wiper blade.
Another disadvantage of the known wiping elements is not only their relatively important volume, but also the fact that in cross-section they show width variations and thus volume variations which are very important and which create problems difficult to be solved when the wiping elements are to be extruded in a continuous manner. Indeed the dimensional tolerances are much easier to be met with when the cross-section of the wiping element shows only small width variations.
As a last disadvantage, not only of the known wiping elements, but also of the known pressure distributing rods, their weak performance when the vehicle moves at high speed can be mentioned. In these circumstances said two elements are subject to a strong air current which flows along the windshield of the vehicle and which tends to lift the wiper blade, the result being first a bad wiping efficiency and then no wiping effect at all. The action of the air flow at high speed is a very complex phenomenon, i.e. said action depends on numerous parameters. One of these parameters is the presence, on the wiping element and/or on the pressure distributing rod, of large surfaces which are substantially parallel to the surface to be wiped.